Consider the question. Christopher Cross "Chris" Griffin is a fictional character from the American animated television series Family Guy. He is the elder son and middle child of Peter and Lois Griffin and brother of Stewie and Meg Griffin. He is voiced by Seth Green and first appeared on television, along with the rest of the family, in a 15-minute short on December 20, 1998. Chris was created and designed by MacFarlane himself. MacFarlane was asked to pitch a pilot to the Fox Broadcasting Company, based on The Life of Larry and Larry & Steve, two shorts made by MacFarlane featuring a middle-aged man named Larry and an intellectual dog, Steve. After the pilot was given the green light, the Griffin family appeared in the episode "Death Has a Shadow".

Answer this question based on the passage: who does chris griffin's voice on family guy?
 What is the step-by-step reasoning process to arrive at the answer: Seth Green?
The relevant information is: He is voiced by Seth Green and first appeared on television, along with the rest of the family, in a 15-minute short on December 20, 1998.